Lasers are used increasingly in various processes including manufacturing processes, and often in materials processing. When a laser is used in a laser enclosure, which may, for example, be a relatively small enclosure cabinet, or a room in a building, the laser beam may be accidentally directly or indirectly incident on the walls, floors, or ceiling of the enclosure for example.
With the development of lasers with higher power it is becoming increasingly challenging to provide a safe containment that protects users and the surrounding environment from injury and damage from stray laser light. Modern high power lasers can readily cut through almost any material including steel and concrete for example.
The damage caused by a stray laser beam may include damage to the surface or appearance of the object, burning a hole right through the object, fire damage, or injury to an operator of the laser or any other person who is in the path of the laser beam. In fact a significant risk could be presented to persons who may be outside a room containing a laser who would be totally unprepared for the sudden emergence of the laser beam through the wall. Furthermore the risk is often heightened as most high power laser beams are infra-red and therefore invisible.
We have previously proposed an active laser guarding system comprising a protective screen provided with an electrically conductive path connected to a fail-safe circuit. If the laser beam is incident on part of the conductive path, the laser beam breaks the conductive path, and the fail safe circuit deactivates the laser beam.
However, it can be a problem with such a system that the path can remain conductive even after being struck by the laser beam, with the result that the fail-safe circuit does not, or does not always, deactivate the laser beam.